Electroconductive resin composition and a videodisc record

ABSTRACT

An electroconductive resin composition is a blend of 5-30% by weight carbon black and a graft-polymer. The graft-polymer is obtained by graft polymerizing 99-76 parts by weight of monomeric vinyl chloride to 1-15 parts by weight of an ethylenevinyl acetate copolymer, the ethylenevinyl acetate copolymer containing 10-65% by weight of vinyl acetate. The electroconductive resin composition has superior heat resistance and mechanical strength and improved flowability and heat stability. The electroconductive resin composition is particularly suitable for preparing video disc records.

This is a division of application Ser. No. 367,988, filed Apr. 13, 1982now U.S. Pat. No. 4,396,660.

DETAILED EXPLANATION OF INVENTION

This invention relates to an electroconductive resin composition, moreparticularly, to a resin composition which has electroconductivity andis prepared by blending carbon black with a graft-polymer prepared bygraft-polymerizing monomeric vinyl chloride to a copolymer of ethyleneand vinyl acetate.

Polymer and copolymer of vinyl chloride are generally of goodweatherability and of high mechanical strength, and have been used forpreparing various shaped articles such as pipes, pipe joints and sheets.Recently, attempts have been made to prepare an electroconductive resincomposition by incorporating an electroconductive filler into thepolymer and copolymer of vinyl chloride. The electroconductive resincomposition has been said to be adapted for preparing videodisc recordof an electrostatic capacity system.

Among the electroconductive fillers, fine metal powders and carbon blackare typical, and the latter has been most widely used. There are manykinds of carbon black. "Ketjen black", manufactured by Akzochemie, hasbeen considered to have a remarkable effect for providing the resin withelectroconductivity and to be most preferred.

As for the polymer and copolymers of vinyl chloride, it has hithertobeen proposed that copolymer of vinyl chloride be used for mixing withthe carbon black (as opposed to the use of polyvinyl chloride, i.e., ahomopolymer of vinyl chloride) to form a material for videodisc records.For example, Japanese Unexamined Patent Publication No. 53- 115104discloses that a resin composition is adapted for manufacturingvideodisc records, which composition is prepared by mixing (1) 44 partsby weight of propylene-vinyl chloride copolymer containing 5% by weightof propylene with (2) 10 parts by weight of vinyl acetate-vinyl chloridecopolymer containing 15% by weight of vinyl acetate and (3) 10 parts byweight of maleic acid ester-vinyl chloride copolymer containing 25% byweight of maleic acid ester, and further by adding thereto anelectroconductive filler. The RCA Review, 1978, March at pages 87 to115, discloses that homopolymers and binary copolymers of vinyl chloridemay be used for preparation of the videodisc records.

It has hitherto been required that a large amount of theelectroconductive material, especially carbon black be incorporated intoa resin of a homopolymer or copolymer of vinyl chloride in order toprovide the resin with electroconductivity. For instance, when 10 partsby weight of said Ketjen black EC is incorporated into 100 parts byweight of the resin, the resulting resin composition has a specificelectric resistance of 10⁵ to 10¹⁰ ω-cm, and when 20 parts by weight ofsaid Ketjen black are incorporated into 100 parts by weight of theresin, the resulting resin composition has a specific electricresistance of approximately 1.0 to 10³ ω-cm. Thus, in order to providethe resin with the electroconductivity the carbon black must beincorporated to count for more than 10% by weight of the composition.When such a large amount of carbon black is added, the resultingcomposition is deteriorated in flowability in a molten state, and showsthe disadvantage that the composition is hard to fabricate. Furthermore,the carbon black tends to deteriorate heat stability of the vinylchloride resin, and the resulting composition becomes deteriorated inthe heat stability thereof.

The inventors contemplated to obtain a resin of a polymer or copolymerof vinyl chloride which maintains its superior inherent properties andis improved in both flowability when molten and heat stability whenheated. For this purpose, the inventors prepared various resins ofpolymer and copolymer of vinyl chloride, mixed carbon black with theresin, and observed the properties of the resulting resin compositions.As a result, the inventors have found that, when the carbon black isadded to a graft-polymer, which is obtained by graft-polymerizingmonomeric vinyl chloride to a copolymer of ethylene and vinyl acetate,the resulting composition is superior in both heat resistance andmechanical strength and furthermore is improved in both flowability andheat stability. Still further, the inventors have found that theresulting composition is improved in impact resistance compared with acomposition using a homopolymer of vinyl chloride. This invention hasbeen made on the findings as mentioned above.

According to this invention there is provided an electroconductive resincomposition which comprises a blend of 5 to 30% by weight of carbonblack and a graft-polymer which is obtained by graft-polymerizing 99 to76 parts by weight of monomeric vinyl chloride to 1 to 15 parts byweight of an ethylene-vinyl acetate copolymer, said copolymer containingtherein 10 to 65% by weight of vinyl acetate.

There are various grades of ethylene-vinyl acetate copolymer availablein the market and the grades are made by the differences in the cotentof vinyl acetate thereof, the averge molecular weight thereof, and thepolymerizing method in which the copolymer was prepared. In general,when the amount of vinyl acetate contained in the copolymer isincreased, the copolymer is improved in compatibility with monomericvinyl chloride but is deteriorated in impact resistance, and adverselywhen the amount of vinyl acetate is decreased, the copolymer is improvedin impact resistance but is deteriorated in compatibility with themonomeric vinyl chloride. Thus the content of vinyl acetate ispreferably limited approximately from 10 to 65% by weight in thecopolymer.

Average molecular weight of the ethylene-vinyl acetate copolymer isnormally expressed by a melt index or Mooney viscosity. Among them, amethod for determining the melt index is provided in ASTM (AmericanStandard of Testing Method) D-1238. Based on the melt index, thecopolymer has a good flowability but an unsatisfactory impactresistance, if it has a melt index more than 100. Conversely, if themelt index is less than 0.1, then the copolymer has a good impactresistance, but an unsatisfactory flowability. These values can bestandards for forecasting the impact resistance and flowability of thegraftpolymer, which is prepared by graft-polymerizing vinyl chloride tothe ethylene-vinyl acetate copolymer.

Further, the ethylene-vinyl acetate copolymer has generally somewhatdifferent properties according to the polymerization process in whichthe copolymer was prepared. However, when the electroconductivecomposition is to be prepared according to the present invention, theprocess by which the copolymer is prepared does not matter at all andprocesses such as suspension polymerization, emulsion polymerization,solution polymerization and high pressure polymerization, can be used.When it is intended to obtain a videodisc record, however, a copolymeris preferably used which is prepared by the solution polymerization andhigh pressure polymerization processes, because the copolymer preparedin said processes normally includes less impurities.

When the monomeric vinyl chloride is graft-polymerized to ethylene-vinylacetate copolymer for use in the present invention, various processesmay be employed such as an emulsion polymerization process, a suspensionpolymerization process, a solution polymerization process and a blockpolymerization process. Among the processes, the suspensionpolymerization process is preferred. The reason for this is that fineparticles can be immediately obtained which can be readily blended withcarbon black to form a uniform mixture. Particulars of a suspensionpolymerization process in which the graftpolymer can be prepared aredisclosed in, for example, Japanese Patent Publication No. 39-27876.According to the disclosures, deionized water, a suspension stabilizersuch as polyvinyl alcohol, a free radical generating agent, and ifdesired an agent for decreasing polymerizaton degree, are charged into ajacketed polymerization vessel, into which ethylene-vinyl acetatecopolymer is then charged and suspended, the air contained in the vesselis discharged, and then vinyl chloride is introduced under pressure intothe vessel. Thereafter, the vessel is heated through the jacket todissolve the copolymer in the monomeric vinyl chloride, andgraft-polymerization is initiated. When the graft-polymerization isinitiated, heat is generated and cooling is carried out through thejacket, thus the polymerization is advanced to a desired extent.Thereafter, remaining monomeric vinyl chloride is discharged out of thevessel and recovered to obtain a slurry including graft polymer. Theslurry is then dewatered, dried, and sieved to obtain fine particles ofthe graft polymer.

When the graft polymer is obtained in the manner as mentioned above, ifanother monomer is present besides monomeric vinyl chloride, thenanother graftpolymer can be obtained in which said monomer and monomericvinyl chloride have been graft-copolymerized to the ethylene-vinylacetate copolymer. The graftpolymer used in this invention may be agraftpolymer in which an additional monomer has been graft-copolymerizedtogether with vinyl chloride to the ethylene-vinyl acetate copolymer.Monomeric vinyl acetate, ethylene and propylene are preferably used asthe said additional monomer. The said monomer is preferably used in anamount less than 10% by weight with respect to the vinyl chloride. Inthe case wherein monomeric vinyl chloride is graft polymerized togetherwith the additional monomer to the ethylene-vinyl acetate copolymer, themonomeric vinyl chloride and the additional monomer should be graftpolymerized totally in an amount from 99 to 85 parts by weight to 1 to15 parts by weight of said copolymer.

The graft polymer should preferably have a particular averagepolymerization degree. If the graft polymer has a very highpolymerizaton degree, it has a very low flowability when molten, andadversely, if the graft polymer has a very low polymerization degree, ithas a very low impact resistance and a very low heat resistance. Theparticular range of the polymerization degree is varied according tointended use. For example, in the case wherein a large amount of carbonblack is incorporated into the graft polymer and precise moulding isrequired as in a videodisc record, the graft polymer should preferablyhave an average polymerization degree from about 300 to 550. In the casewherein it suffices to add a small amount of carbon black as in thepreparation of packaging materials which are antielectrostatic and arehard to be electrified, the graft polymer should preferably have apolymerization degree as high as about 700, because the graft polymer ofhigh polymerization degree produces advantageously a product of highmechanical strength.

In order to blend carbon black with the graft polymer to prepare theresin composition, usual blending apparatus may be used. Since thecarbon black is generally small in bulk density and tends to agglomeratetogether, attention must be paid to agitate to disperse it uniformly inthe resin. For example, a blending apparatus such as a Henschel Mixershould be preferably used which can provide the resin with high shearenergy. Furthermore, according to the technique as taught by JapaneseUnexamined Patent Publication No. 55-158919, preferably the carbon blackmay be at first made into fine particles less than 0.044 mm in diameter,which are then added gradually to the graftpolymer particles. Thoughthere are many kinds of carbon black as mentioned above, the carbonblack is normally added to the resin in an amount of 10 to 30% byweight.

Since the graft polymer is a polymer prepared from monomeric vinylchloride, it tends to be decomposed by the heat given for the purpose offabrication. Thus, in order to make it easy to fabricate the polymer,various additives such as stabilizers and lubricants may be preferablyadded which have hitherto been added. Besides the additives, a smallamount of other resins may also be added. For instance, methylmethacrylate-styrene-butadiene copolymer, or chlorinated polyethylene,which are normally used in order to elevate impact resistance ofpolyvinyl chloride, may be added. Furthermore, other polymers orcopolymers of vinyl chloride may also be added thereto. The resins suchas "Telalloy" (Trade Mark) manufactured by Kanegabuchi Kagaku in Japanand "PN Resin" (Trade Mark) manufactured by Showa Denko in Japan, whichare normally added in order to elevate heat resistance of polyvinylchloride, may be added thereto. These polymers, copolymers or resinsshould be employed in the amount less than 20% by weight, preferablyless than 10% by weight, based on the amount of the graft polymer. Whenadditives are to be added, special attention should be paid to the kindsand the amounts of the additives. This is because, for example, in thecase wherein a videodisc reocord is intended to be obtained, theadditives are sometimes built up on the surface of a stamper while thevideodisc record is produced, and as the result the videodisc recorddoes not provide a clear picture.

The above-mentioned mixture is then kneaded to form a uniformcomposition, which is electroconductive. The composition, when comparedwith the case wherein homopolymer or binary copolymer of vinyl chlorideis used, has the advantages that the composition can be easilyfabricated due to excellent flowability when molten, notwithstanding thehigh heat resistance, and further that a product of the composition ishard to be broken due to excellent impact resistance. Thus the productof the composition is hard to be charged with static electricity owingto its own electroconductivity, and accordingly does not attract dust,and is adapted for use in packaging materials. Furthermore, since thecomposition is easily fabricated, it can be formed without difficultyinto a disc having minute and delicate grooves, in addition thecomposition has excellent heat resistance and impact resistance, andtherefore is best suited for preparing a videodisc record. Consequently,varied applications can be expected in this aspect.

As for the heat resistance of the vinyl chloride polymer, thegraftpolymer is generally inferior in heat resistance to thehomopolymer, however, the resin composition according to the inventionis superior in heat resistance to the usual resin composition preparedby blending the homopolymer with carbon black in the same rate. This isquite unexpected. The reasons for this cannot be well understood.However, when solubility of the resin composition in tetrahydrofuran isinvestigated, the composition having a high heat resistance shows anincreased insolubility and is supposed to be partly cross-linked. Moreparticularly, according to conventional manners, when use is made of apolymer or copolymer of vinyl chloride alone or a mixture of saidpolymer or copolymer with ethylene-vinyl acetate copolymer, and whensaid polymer, copolymer or a mixture thereof is mixed further withcarbon black to form an electroconductive composition, the compositionis easily soluble in tetrahydrofuran. To the contrary, the resincomposition according to this invention, wherein use is made ofgraftpolymer of vinyl chloride, is sparingly soluble in tetrahydrofuran.Therefore, the resin composition according to this invention should beconsidered not to be a simple mixture of a polymer and carbon black.

By way of Examples, this invention is explained to the full particulars.

EXAMPLE 1

At first, the following describes the general preparation of the graftpolymer used as a raw material.

Into a polymerizaton vessel, capable of withstanding a pressure of 60Kg/cm² G, having an inner volume of 160 liters, and provided with ajacket and stirrer, were charged deionized water, a polyvinyl alcoholderivative, dispersing agent, organic peroxide derivative free radicalgenerating agent and a copolymer of ethylene and vinyl acetate. Thevessel was then closed tightly, the air remaining in the vessel wasdischarged, monomeric vinyl chloride and another monomer were chargedinto the vessel, and suspension polymerization was carried out toprepare a graft polymer.

After the polymerization reaction was completed, the remaining monomerswere recovered, dewatered, and dried to obtain particles of polymer,which particles were then sieved through a 32 mesh sieve to collect thefine particles. The fine particles are the desired portion of graftpolymer. The graft polymer has the constituents and the averagepolymerization degree listed in Table 1 hereinbelow. In the Tablehereinbelow, EVA represents a copolymer of ethylene and vinyl acetate,VAC represents the content of vinyl acetate, and MI the melt index.

                  TABLE 1                                                         ______________________________________                                        Constituent of Graft Polymer                                                  Constituent of Graft Polymer                                                  (% by weight)                                                                                   Content of        Average                                                     monomer           poly-                                                       other than Content                                                                              merization                                     Kind and amount                                                                            vinyl      of vinyl                                                                             Degree                                    No.  of EVA       chloride   chloride                                                                             (JIS K-6721)                              ______________________________________                                         1   Ultrathene 6     --       94     360                                          634*                                                                      2   Ultrathene 6     --       94     360                                          760                                                                           VAC 40%                                                                       MI 65                                                                     3   Ultrathene 5     Ethylene 93     400                                          634              2                                                        4   Ultrathene 6     Propylene                                                                              90     400                                          634              4                                                        5   Ultrathene 6     Vinyl    88     400                                          634              Acetate                                                                       6                                                        6   Ultrathene 6     Ethylene 1                                                                             91     360                                          634              Propylene 2                                              7   Levapren** 6     --       94     360                                          450P                                                                      8   Evathlene***                                                                             10    --       90     400                                          410P                                                                      9   Soarlex****                                                                              10    --       90     400                                          CH                                                                       10   Ultrathene 10    --       90     700                                          634                                                                      ______________________________________                                         *EVA manufactured by a high pressure method by Toyo Soda Manufacturing Co     Ltd. in Japan, containing 26% of vinyl acetate and having a melt index of     4.                                                                            **EVA manufactured by a solution polymerization method by Bayer Co. in        West Germany, having a VAC of 45% and having a Mooney viscosity of 20.        ***EVA manufactured by an emulsion method by Dainippon Ink and Chemicals      Co. in Japan, having a VAC of 60% and having a melt index of 1.               ****EVA manufactured by a suspension polymerization method by Nippon          Synthetic Chemical Industry Co. having a VAC of 60% and having a melt         index of 15 to 50.                                                       

Carbon Black was added to each of said graft polymers at the mixing rategiven in Table 2 hereinbelow to obtain a resin mixture.

                  TABLE 2                                                         ______________________________________                                        Mixing rate                                                                                      Weight  Parts by                                           Compounds to be mixed                                                                            (g)     weight                                             ______________________________________                                        Graft Polymer      1500    100                                                Dibutyl Tin        20      1.3                                                Mercaptide                                                                    Dibutyl Tin        10      0.67                                               Laurate                                                                       Lubricant of amide 23      1.53                                               Derivative                                                                    Lubricant of Monogry-                                                                            23      1.5                                                ceride Derivative                                                             Carbon Black       300     20                                                 (Ketjen black EC)                                                             ______________________________________                                    

In mixing, the resin was charged into a 10 liter Henschel mixer andmixed therein, carbon black being added during mixing. The temperaturewas elevated up to 50° C., the carbon black was dispersed uniformly,thereafter the stabilizer and lubricant were added thereto. Thetemperature was kept at 50°-60° C., and mixing was continued for 5minutes. Thereafter the resulting mixture was cooled and removed fromthe mixer. Then l50 g of the mixture was kneaded by two rolls of 8 inchdiameter to form a sheet of 0.5 mm thickness.

Thereafter, the sheet was interposed between ferro-type plates andpressed therein to obtain a sheet of 1 mm thickness having smoothsurfaces. Further, test pieces for measuring heat resistance wereprepared by press moulding, and using these pieces, there were measuredflowability when molten, heat resistance, heat stability, bendingstrength, impact resistance, electroconductivity and hygroscopicity.Respective testing methods are explained hereinbelow.

Flowability when molten : The sheet was cut into a square sheet of 2 mm×2 mm, which was charged into a Koka type flow tester. There wasprovided a nozzle of 1 mm φ×10 mm, through which molten sheet wasextruded under a pressure of 150 Kg/cm² at a temperature of 180° todetermine the flowability.

Heat resistance : The sheet obtained by press moulding was testedaccording to the testing method provided in ASTM D-648 (using load of18.6 Kg).

Heat stability : The sheet was put into a gear oven at 170° C., and theheat stability was estimated by the period of time elapsed until thesheet began to form.

Bending Strength : This was measured according to the method provided inASTM D-790 (measuring temperature 20° C.) using the press moulded sheet.

Impact Resistance : The press moulded sheet of 1 mm thickness was cutinto squares having sides of 2 cm in length, and each of the squaresheets was used for a test piece. The test piece was set in a Du Ponttype impact tester, and was observed under the following conditions:

    ______________________________________                                        Impacting         forward end is rounded in                                                     the radius of 1/2 inch                                      Floor             flat                                                        Weight            300 g                                                       Height            2.5 cm                                                      Measuring temperature                                                                           20° C.                                               ______________________________________                                    

Estimation

Tests were made using 12 test pieces, and the results were expressed bya numerical value based on the following standards:

0 : not broken

1 : cracked

2 : broken but not to pieces scattered into pieces

3 : broken and scattered into pieces

Electroconductivity : A press moulded sheet of 1 mm thickness was cutinto a rectangular sheet of 10 mm in width and 70 mm in length, whichwas used as a test piece. End portions extending 10 mm in length fromboth ends were polished by a sand paper, silver paste was then appliedthereto, and the test piece was left in a room at 50% relative humidityfor 24 hours. Thereafter, direct current voltage was applied to measurethe electroconductivity.

Hygroscopicity : A square test piece of 5×5 mm was cut from a pressmoulded sheet having smooth surfaces and was left for 6 hours in a roomof 95% relative humidity at 50° C. Thereafter the test piece wasobserved to find extraordinarily foamed pores by means of an opticalmicroscope. The thus investigated results are listed in Table 3hereinbelow.

                                      TABLE 3                                     __________________________________________________________________________    Results of observed properties                                                    Flowability                        Hygro-                                     when molten                                                                          Heat  Heat Bending                                                                            Impact                                                                             Electro-                                                                             scopicity                              Resin                                                                             10.sup.-2                                                                            Resistance                                                                          Stability                                                                          Strength                                                                           Strength                                                                           conductivity                                                                         Number                                 No. cm.sup.3 /sec                                                                        °C.                                                                          Minutes                                                                            Kg/cm.sup.2                                                                        --   Ω-cm                                                                           of Pores                               __________________________________________________________________________    1   0.9    69    120  460  1.5  5      0                                      2   1.0    68    110  450  2.2  7      0                                      3   1.6    62    120  440  1.3  8      0                                      4   1.4    64    140  490  1.2  8      0                                      5   1.1    65     80  500  0.9  5      0                                      6   1.7    63    130  460  1.7  6      0                                      7   0.9    69    120  460  1.5  6      0                                      8   0.7    65    120  520  2.7  7      3                                      9   0.8    65    120  530  2.7  7      5                                      10  0.02   72    140  650  0.0  7      0                                      __________________________________________________________________________

From Table 3 the following can be seen. The resin No. 10 in Table 3 hasa low and inferior flowability because of a high polymerizaton degree,in contrast, the other resins have a high and superior flowability. Thatis, if the polymerizaiton degree is decreased, then the flowability isincreased and improved, and if monomeric propylene or vinyl acetate isgraft-polymerized together with monomeric vinyl chloride, then theflowability is increased. In spite of the increased flowability, theresins in Table 3 have all a high heat resistance and excellentelectroconductivity. Further, when use is made of the ethylene-vinylacetate copolymer prepared by an emulsion polymerization method (as inresin No. 8) or by a suspension polymerizaion method, the resultinggraftpolymer has a high hygroscopicity and becomes inferior. When use ismade of the ethylene-vinyl acetate copolymer having a low averagepolymerization degree, the resulting graftpolymer becomes ratherinferior in impact resistance.

EXAMPLE 2

In this Example, preparation of graftpolymers and evaluation of the thusprepared graftpolymers were carried out in the same manner as in Example1, Resin Nos. 1 and 10, except that use was made of 9 parts by weight ofcarbon black instead of 20 parts by weight of carbon black in Table 2 toform the mixture. The results are listed in Table 4.

                                      TABLE 4                                     __________________________________________________________________________    Results of observed properties                                                                                     Hygro-                                                                        scopi-                                       Flowability                 Electro-                                                                           city                                         when molten                                                                          Heat re-                                                                           Heat Sta-                                                                          Bending                                                                            Impact re-                                                                          conduct-                                                                           Number                                   Resin                                                                             10.sup.-2                                                                            sistance                                                                           bility                                                                             strength                                                                           sistance                                                                            ivity                                                                              of                                       No. cm.sup.3 /sec                                                                        °C.                                                                         minutes                                                                            kg/cm.sup.2                                                                        --    Ω-cm                                                                         Pores                                    __________________________________________________________________________     1  4.5    69   150  530  0.3   3 × 10.sup.8                                                                 0                                        10  0.3    73   170  700  0.0   7 × 10.sup.8                                                                 0                                        __________________________________________________________________________

From Table 4 it can be seen that, in the cases wherein use is made of 9parts by weight of carbon black, the resulting resin composition has notsuch a high electroconductivity that the composition can be used forpreparing a videodisc record, but has sufficient electroconductivity sothat the composition is adaptable for preparing a packaging material foruse in preventing accumulation of an electrostatic charge. The resins inTable 4 have high heat resistance in spite of high flowability, and alsohave high impact resistance.

Comparative Example 1

In this Comparative Example, use was made of various resins outside ofthe scope of the present invention, and resin mixtures were prepared inthe same manner as in Example 1, wherein the corresponding graftpolymersoutside of the scope of the invention are listed in Table 5 hereinbelow.

                  TABLE 5                                                         ______________________________________                                        Resin                                                                                                             Polymer-                                  Resin                     Constituent                                                                             ization                                   No.   Resin Name          (Weight %)                                                                              Degree                                    ______________________________________                                        21    PVC Homopolymer     VC = 100  360                                             manufactured by                                                               Tokuyama Sekisui K.K.                                                   22    Vinyl chloride-Vinyl Acetate                                                                      VC = 88   450                                             copolymer manufactured by                                                                         VAC = 12                                                  Nippon Zeon K.K. 400 × 150 P                                      23    Vinyl chloride-Ethylene                                                                           VC = 99   430                                             copolymer manufactured by                                                                         Et = 1                                                    Tokuyama Sekisui K.K.                                                   24    Vinyl chloride-Propylene                                                                          VC = 93   450                                             copolymer manufactured by                                                                         Pr = 7                                                    Air Products and Chemicals                                                    Co.                                                                     25    Graftpolymer by grafting                                                                          VC = 80   400                                             Vinyl Chloride to Ultrathene                                                                      EVA = 20                                                  634                                                                     26    Resins blended resin No. 21                                                                       PVC = 94                                                  with Ultrathene 634 EVA = 6                                                   (Note 1)                                                                ______________________________________                                    

(Note 1) 1000 g of homopolymer of vinyl chloride in Resin No. 21, 60 g(in pellet form) of Ultrathene 634 and 2 liters of water were charged inan autoclave, the air was removed, 1 kg of monomeric vinyl chloride wasthereafter charged, and the resulting mixture was heated at 50° C. for 2hours to dissolve the Ultrathene. Thereafter the remaining monomericvinyl chloride was discharged, water was removed, and the resultingproduct was dried to obtain a fine particulate mixture of vinyl chloridepolymer particles and Ultrathene particles.

Using each of the resin in Table 5, a mixture was prepared in the samemanner as in Example 1, then the properties of thus obtainedcompositions were evaluated in the same manner as in Example 1. Theresults are listed in Table 6.

                                      TABLE 6                                     __________________________________________________________________________    Results of observed properties                                                    Flowability                 Electro-                                                                           Hygro-                                       when molten                                                                          Heat Re-                                                                           Heat Sta-                                                                          Bending                                                                            Impact Re-                                                                          conduct-                                                                           scopicity                                Resin                                                                             10.sup.-2                                                                            sistance                                                                           bility                                                                             strength                                                                           sistance                                                                            ivity                                                                              Number                                   No. cm.sup.3 /sec                                                                        °C.                                                                         minutes                                                                            kg/cm.sup.2                                                                        --    Ω-cm                                                                         of pores                                 __________________________________________________________________________    21  0.6    68   100  410  2.9   8    0                                        22  1.2    64    40  470  0.5   7    0                                        23  0.5    66   110  410  2.3   7    0                                        24  1.8    56   150  490  0.7   9    0                                        25  1.6    63   120  500  0.0   6    0                                        26  1.2    69   100  480  3.0   5    0                                        __________________________________________________________________________

When the results in Table 6 are compared with the results in Table 3,the compositions according to this invention are totally superior to thehitherto known compositions. Especially in respect of heat resistance,for example, when Resin No. 1 is compared with Resin No. 21, if theresin itself is observed, a graftpolymer of vinyl chloride is inferiorin heat resistance to a homopolymer of vinyl chloride, however, ifcarbon black is mixed with the resin and kneaded to form a composition,then the heat resistance is reversed between the graftpolymer and thehomopolymer, and the resulting graft polymer composition has a superiorheat resistance compared with that of the homopolymer composition.Nevertheless, the graftpolymer composition has an better flowabilitythan the homopolymer composition. This result is unexpected.

Furthermore, when Resin No. 1 is compared with Resin No. 26, it can beseen that the graftpolymer prepared by grafting vinyl chloride to EVA issuperior in impact resistance to the resin mixture prepared by blendingthe homopolymer of vinyl chloride with EVA. This fact shows that theresin composition according to this invention brings about a remarkableeffect.

Still further, among the resin compositions according to this invention,when use is made of an ethylene-vinyl acetate copolymer, which isprepared by a solution polymerization method or a high pressurepolymerization method, and when monomeric vinyl chloride alone isgrafted to said ethylene-vinyl chloride copolymer to obtain agraftpolymer or when a monomer mixture of vinyl chloride and ethylene,propylene, or vinyl acetate is graft polymerized to said ethylene-vinylacetate copolymer to form a graftpolymer, the resulting graftpolymer isadapted for use in preparing a videodisc record.

I claim:
 1. An electroconductive resin composition consistingessentially of blend of 5 to 30% by weight of carbon black and agraftpolymer which is obtained by graft-polymerizing 99 to 76 parts byweight of monomeric vinyl chloride to 1 to 15 parts by weight of anethylene-vinyl acetate copolymer, said copolymer containing therein 10to 65% by weight of vinyl acetate.
 2. An electroconductive resincomposition according to claim 1 wherein the graft-polymer has apolymerization degree between 300 and
 550. 3. A electroconductive resincomposition according to claim 1 or 2 wherein the ethylene-vinyl acetatecopolymer is prepared according to either a high pressure polymerizationmethod or a solution polymerization method.
 4. An electroconductiveresin composition according to claim 3 wherein the graft-polymer is apolymer obtained by graft-polymerizing to said ethylene-vinyl acetatecopolymer simultaneously the monomeric vinyl chloride and less than 10%by weight based on the monomeric vinyl chloride of a monomer selectedfrom the group consisting of monomeric ethylene, propylene and vinylacetate.